ES′SENCE. Syn. Essentia, L. The active and characteristic portion of a substance, or that on which its most remarkable properties depend. The term has been very loosely applied to various preparations presumed to contain these essential principles or qualities, disencumbered of grosser matter. Modern systematic writers generally restrict its application to the volatile oils obtained from vegetable substances by distillation, or to a strong solution of them in alcohol. In pharmacy and perfumery, the word ‘essence’ is applied to concentrated preparations that differ vastly from each other. Thus, concentrated effusions, decoctions, liquors, solutions, and tinctures, are frequently called ‘essences’ by those who vend them; but the term ‘fluid extracts’ would be more appropriate, if those already mentioned are not deemed sufficiently showy and attractive. We shall here confine ourselves to a brief notice of the principal compound essences, or those that undergo some preparation beyond being merely extracted from vegetables by distillation along with water. The latter will be considered under the article Oil.
The concentrated preparations of the pharmaceutist, termed ‘essences,’ are mostly prepared by digesting the active ingredient or ingredients in rectified spirit of wine, either with or without the addition of a certain portion of water; or they are extemporaneously formed by dissolving a portion of the essential oil of such substances in the spirit. In this way are made the essences of lavender, musk, ginger, &c. When it is desired only to obtain the aromatic and volatile portion of the ingredients, the latter are usually digested in the spirit for a few days, and then submitted to distillation, when the alcohol comes over loaded with aromatic essential oil, or other volatile matter. In this way are prepared most of the fragrant essences of the perfumer and druggist, when simple solution of the essential oils in alcohol is not resorted to. In many cases the active principles of the ingredients are partly volatile and partly fixed, or at least do not readily volatilise at the temperature at which alcohol distils over. This is the case, for instance, with the active portion of ergot and Jamaica ginger. In such cases digestion alone should be adopted. When the principles of organic substances, of which it is desired to obtain a concentrated solution, are resinous or oily, or little soluble in weak spirit (which is mostly the case), the strongest rectified spirit of wine should alone be employed. In the preparation of essences without distillation, the method by percolation or displacement is preferable to that of simple maceration and expression, when the nature of the ingredients and other circumstances render it applicable, as it is not only more economical, but a more concentrated solution may thereby be obtained. At the same time, however, the reader should remember, that this mode of operating requires much greater experience and skill to ensure success than the former method. This clumsiness of manipulation is the common cause of the failures which are so frequently met with in the preparation of these articles.
The ingredients for the preparation of essences must undergo the same operations of bruising, powdering, or slicing, as directed under ‘Tincture,’ previous to digestion in the spirit, or other menstruum; and the length of time they should be allowed to infuse, when this method alone is adopted, should not be less than ten days; but this time may be advantageously extended to a fortnight, or even longer. During the whole of this period frequent agitation should be employed, and when the ingredients are so bulky as to absorb the whole of the fluid, the vessel which contains them should be securely fastened by a bung or stopper covered with bladder, and inverted every alternate day. By this means every portion of the ingredients will be equally exposed to the action of the menstruum. In all such cases the method of displacement, or percolation, is preferable. For the essences used as perfumes and for flavouring, not only must the spirit be perfectly tasteless and scentless, but it must be also quite devoid of colour.
The following formulæ embrace most of the essences met with in the shops. Those not found among them may be readily prepared by applying the general directions given above, or by employing the formula given for the preparation of the essence of some similar substance, merely varying the characteristic ingredient. Thus, were it desired to form an essence of ambergris or of myrrh, and no formulæ could be found for these preparations, the tyro would consider in what menstruum the active principles of these substances were most soluble. This, he would immediately see by reference to their properties, is rectified spirit of wine. He would next have to decide on the proper strength of his essence. In this he must be guided, either by the strength of the like preparations of other makers, or by his own judgment of what would be useful, novel, or convenient. Suppose he decided that his essence should represent 1-10th of its weight of the solid ingredient. He would then take 2 oz. of ambergris or myrrh, and 20 oz. of rectified spirit, which he would digest together for 10 days or a fortnight in the manner described above. Had the required preparation been an essence of senna (for example), he would probably recollect, or might easily ascertain by reference, that the active properties of senna are soluble in both water and weak spirit. Then, to make an essence 4 times as strong as the tincture of the pharmacopœia, 7 oz. of senna, and 1 pint of proof spirit, should be employed, with due digestion, as before.[280] The same applies to other preparations. See Concentration, Decoction, Infusion, Liquor, Spirit, Tincture, &c.
[280] See directions given under Tincture.
Essence of Ac′onite. Syn. Essentia aconiti, L. Prep. From aconite (herb, dried, and powdered), 8 oz.; rectified spirit, 16 oz.; macerate for 4 days at a temperature of 68° Fahr., press, and strain; the marc or residuum is again macerated with (a little) spirit, and pressed as before, so that the weight of the mixed tinctures may amount to double that of the herb.—Dose, 3 to 6 drops. See Tincture.
Essence of All′spice. Syn. Essence of pimento; Essentia pimentæ, L. Prep. From essential oil of pimento or allspice, 1 fl. oz.; strongest rectified spirit of wine, 1 pint; agitate until perfectly united, and the next day decant the clear portion, if there is any sediment. Used to make pimento water, and by cooks and confectioners as a ‘flavouring.’
Essence of Al′monds. Syn. Essence of bitter almonds, E. of peach kernels, E. of ratafia, E. of noyeau, Quintessence of n., Almond flavour; Essentia amygdalæ, E. a. amaræ, L. Prep. 1. From essential oil of almonds, as the last.
2. (Pereira.) Essential oil of almonds, 1 fl. oz.; rectified spirit, 7 fl. oz.
Uses, &c. It is added to wine, cordials, perfumery, pastry, &c., to impart an agreeable nutty flavour or aroma. It is also employed to prepare cherry-laurel, peach-kernel, and bitter-almond water. A large quantity is consumed by the confectioners, and by wine merchants to ‘improve’ their sherries, and to give Cape wine a sherry flavour. It should be used in very small quantities, as it is very powerful, and, in quantity, poisonous. A few drops are sufficient for several pounds of pastry. The first formula is that used in trade. The second is sometimes used by the druggists, and is occasionally vended under the name of ‘CONCENTRATED ESSENCE OF BITTER ALMONDS,’ &c. The directions for purifying the almond oil from hydrocyanic acid before dissolving it in the spirit, given in more than one recent book of receipts, are absurd, as in this way the oil loses much of its characteristic odour and flavour, and by keeping gradually becomes nearly destitute of both. See Essential Oil.